From Cardiff, you probably have a 1hr ride (5miles+getting lost), then 2 hrs+ of rail to Gloucester.
I dont think you will be in any condition to ride a bike on the wrong side of the road after a read-eye flight. It usually takes me 30-45 mins to get my bike roadworthy again after a flight. With rail travel, you just need to have it "roll-worthy" and can fix it up on the train.
A warning though, Gatwick train terminates at London Victoria.
The Reading line leaves from Paddington Station, which is a 2 mile ride across central London .
From the "Tourist Info" sign, just S of Buckingam Palace, go 1/2 mile North to Hyde Park. Cross to the top of the park and head North to where you see the railway (BW line) terminate. Hyde Park is OK for cycling.
There may be a rounderbout rail link to Reading, do you know of one?
The only bit of S Europe I have toured is Slovenia in September, a lovely little country.
Last edited by MichaelW; 01-14-05 at 12:46 PM.